Fuel pump



F. C. MOCK Feb. 23, 1937.

-FUEL PUMP Filed Oct. l1, 1932 I N VEN TOR.

Iliff/ll.

www N M/m @.n A Mm Uw `Y B W Patencedreb. 23, 193'? FUEL PUMP y Frank C.Mock, Montclair, N. J., assignor, by

' mesne assignments, to Eclipse Aviation Corporation, East Orange, N.J., a corporation lof New Jersey Application October 11, 1932,"SerialNo. 637,341

9 claims. (el. 10a-zas) This invention relates to pumps and moreparticularly to liquid pumps adapted to meter and force fuel to thecombustion chamber of an internal combustion engine.

The present application is a continuation in part of my co-pendingapplication, Serial No. 546,122, flied June 22, 1931.

It has heretofore been suggested to construct multi-cylinder fuel pumpsin a manner to have 10 an individual operating member or cam for eachpump piston. In the usual construction of engine fuel pumps the amountof fuel forced at each stroke yof the piston is small, and it istherefore difficult to construct a plurality of cams with 15 suchaccuracy as to eliminate objectionable variations in fuel chargesbetween the individual engine cylinders. Unequal fuel charges produce 1unequal combustion pressures which cause engine vibration and generallyunsatisfactory op- 20 eration.

An object of the present invention is to provide a multi-cylinder fuelpump in which all the pistons are actuated'by a sin'gle cam preferablyarranged centrally of the fuel pump cylinders.A In 25 this arrangementthe same cam operates all of the pistons, and therefore variations instroke are obviated.

Another object of the invention is to provide a compact multi-cylinderpump which is easy to manufacture and in which the body portion may beformed of a lightmetal, such as aluminum, within which the individualpump cylinders, preferably constructed of steel, mayl bev readilyassembled. u

Another object, of the invention is to provide a fuel pump which isself-priming.

Another object of the invention is to provide a fuel pump in whichoccluded gases are readily eliminated from the cylinders.

Another object of the invention is to provide a fuel pump in whichparticles of foreign matter are ejected therefrom and returned to themain supply tank.

. Another obj'ect of the invention is to provide a 45 fuel pump in whichfuel leakage past the piston is returned to the supply tank withoutbeing subjected to pump pressure.

Another object of the invention is to provide a fuel pump which isvented to the supply tank 50 during the intake stroke, whereby occludedgases may be ejected from the cylinder during the intake cycle.

A feature of the illustrated embodiment of the invention relates to anarrangement of pump cyl- 55 inders around a elltral power driven camwhich ator.

rected to the outlet from a central supply cham.

ber preferably fed by means of a pressure pump drawing fuel from themain tank. Means are also provided in the central supply chamber formedin the pump for straining the fuel and returning gases and dirtparticles therefrom to the main tank.

Other objects and features of the invention will be apparent from thefollowing description of a preferred embodiment, of the invention inconnection with which reference may be had to the accompanying drawingin which,

Fig. 1 is a sectional view of the improved pump, and a diagrammaticarrangement thereof for use on an engine, the engine cylinder and supplytanks being' drawn to a somewhat smaller scale,

Fig. 2 is an enlarged perspective view of the washer used to positionthe spring of the pump cylinder outlet valve for preventing accumulationof gases atthe upper end of the spring, and

Fig. 3 is an end view yof the operating cam, as viewed on line 3-3 ofFig. 1.

4Referring to the drawing, the fuel pump is provided with a housing I Iwithin which-is an operating shaft I2 mounted in suitable bearings I3and -I4 and having a tapered cam I6 slidabls7 'mounted thereon which isadapted to be rotated by the shaft I2 and to be axially slidable thereonby a manually operated lever I'I through a yoke I8 positioned withingroove 20. Lever I'I is pivotally mounted within the housing II by shaftI9 and is adapted to be manually rotated by any suitable means (notshown).

Shaft I2 is rotated in timed relation with the engine, one cylinder ofwhich is shown at 2I, by a shaft 22 mounted in the housing I I bybearings 23 and having a gear 24 adapted to mesh with an engine drivengear (not shown). The opposite end of shaft 22 is provided with gear 21in mesh with gear Zsecured to shaft I2. The main portion of housing IIis divided on a plane at right angle to the axis of shaft I2, the upperand lower portions 29 and 3| respectively being secured together by aplurality of screws 32.

' Within the upper portion 29 are arranged a plurality of pump cylinders34, the number of cylinders used being dependent on the number ofcylinders in the engine upon which the pump is installed. Both portions29 and 3| of housing are preferably constructed of a light material suchas aluminum in order to reduce the weight for aircraft operation, andeach of the cylinders 34 is preferably formed of a stronger materialsuch as steel in order to have the cylinders impervious to fuel underhigh pressure. The cylinders are insertable from the inside of housingportion 29 and provided with a. collar 36 for locating them therein, anut 31 being threaded upon the upper end of cylinder for clamping it tothe housing. Outlet valve 38, normally pressed against the tting 39 by aspring 42is preferably positioned in the upper end of the cylinder andacts as a check valve to prevent fuel from being returned to the pumpcylinder after it has been forced through the valve by the action ofpiston 43. A threaded cap 44 holds valvel 38 and spring 42 in position,and a discharge conduit 46 is secured to the cap 44 by a nut 41. Theupper end of spring 42 is preferably positioned in cap 44 by a novelwasher 48, shown in Fig. 2, which has ears 49 and 5|, the upturned ears49 acting to space the washer 48 from the upper end of the recessholding the spring 42, and the downturned ears being adapted to spacethe spring 42 from the sidewalls of the cap. It may be observed that inthis construction the spaces 52 between adjacent ears of the washer actas passageways for gases accumulating within the outlet passagewherefrom they may readily pass upwardly through the outlet conduit 46and the injection nomle 54 to the engine cylinder 2|.

.Piston 43 is preferably provided with a reduced upwardly projectingportion 56 within which is a passage... 51 adapted to vcommunicate witha groove 58 formed in the side wall of the cylinder 34 whereby thecylinder gases are vented. Each pump cylinder is fed by means of aninlet port 59 adapted to be uncovered by piston 43 toward the lower endof its stroke, the port being in communication with a downwardlyextending passage 6|v which is in communication with a central supplychamber 62 formed in thegbody of the pump. The supply chamber 62 is fedfrom the main supply tanks 63 and 64 by meansof an engine drivencirculating pump 66 which draws its supply from one or the other tanksof 63 and 64 through conduit 61 or 68, valve 69 and conduit 1|. Theoutlet from pump 66 is connected with the central supply chamber 62 by aconduit 13 and tting 14.

As the fuel is delivered from pump 66 it passes upwardly through screen16 to chamber 62 and through passage 6I to each of the individual pumpcylinders, one of which is shown in Fig. 1

vin position to receive a fuel charge. The central 82 secured to thecover 11 by fitting 844 and which tubular member projects downwardly toa point adjacent the screen 16, the purposes of which are hereinaftermore fully described, All Opening 9| is preferably formed in fitting 62adjacent the upper portion of chamber62 through which gases accumulatingin the upper part of the chamber may readily pass through the outletvalve 19 to the main tank.

Pistons 43 are normally urged to their lower position by springs 92 andare providedwith adjusting screws 93. Reciprocation of the pistons isaccomplished by-bell crank levers 94 pivotally mounted'on the housing at85, one end of which contacts with adjusting screw 93 through roller 96and the other end of which contacts with slidable cam I6 by means ofmember 98 preferably having a rotatable spherical outer surface wherebyfriction is reduced to a minimum. Groove 58, which is adapted tocoincide with the lower portion of passage 51 formed in piston h43, isconnected to the return conduit 8| by a passageway 99 formed in the bodyof the housing I I and preferably connected to the return conduit 8| onthe return side of relief valve 19. The housing |I is preferablyprovidedwith a plurality of openings |0| through which the clearance betweenadjusting screws and bell cranks 94 may be observed and the adjustmentvaried if necessary. The openings, if desired, may be normally closed bya transparent removable cover |02. f

In the operation of the pump, the two-way valve 69 will be positioned ineither of its operative positions, depending from which of the maintanks it is intended to supply` the fuel pump. In the positionshown inFig. 1, valve' 69 is shown in the full line position as connecting tank64 with the pump 66, from which fuel will be forced through passage I04, screen 16, passage 6I, and

It is preferred to maintain the pressure within chamber 62 at somepredetermined pressure, for example three pounds, whereby when piston 48reaches the position shown in Fig. 1, fuel will be forced into the pumpcylinder under pressure and the gases inthe upper portion of thecylinder will be forced out of the cylinder and will pass downwardlythrough passage 51 and from thence outwardly through return conduit 8|lto the through inlet port 59 into the pump cylinder.

vented main supply tanks. Reciprocation jofa piston 43 in the upwarddirection will rstcut oi! communication between passages 51 and 99 andshortly thereafter will close port 59. The total clearance space betweenthe piston and the upper` gases within the cylinder will be forced intothef discharge passage 46 and on the next intake stroke of the pistonthe cylinder will be completely lled with fuel and that any gases whichcollect within the cylinder because of absorption in the fuel piston,the compression pressure of air alone is insumcient to openv check valve38. 'I'his is very desirable for it prevents the pump from forcing airto the engine after a failure of the fuel supply. .Although it isintended that screen 16 will pre- 3. A fuel pump comprising asubstantially, vertical cylinder having an outlet in its top wall,`

vent the major portion of all foreign particles from reaching chamber 62in ordinary constructions, this is ordinarily' impossible to doycompletely, and for this reason tubular member 82 is projecteddownwardly to a point adjacent the screen. Pump 66 is preferablyconstructed with a capacity greater than that necessary to feed theindividual pump cylinders and the excess will be forced through thetubular -member 82 at considerable velocity which will cause particlespassing through the screen to be ejected past relief valve 19 and intothe supply tanks.

Cam I6 is shown in Figs. Land 3 as positioned to give the maximumstrokeof piston 43, but if it should be desired to reduce the capacityof the pump, lever I1 is rotated in a counterclockwise direction,whereby cam I6 will be moved downwardly, and the tapered portion |08will actuate the piston 43 at a less stroke for each rotation of thecam. The leading surface |09 of cam I6 is preferably parallel to theaxis of shaft I2, whereby the port 59 is closed by the piston at thesame point in the cam cycle regardless of its axial position. It is notessential that the cam be constructed in this manner, but it ispreferred to do so in order to have the fuel injection occur at the samepoint in the engine cycle irrespective of the amount of fuel injected.

It may be readily observed from the above 30 description that animproved fuel pump has been provided in which provision is made forforcing fuel into the pump cylinder at each stroke thereof, and that theincoming fuel may force occluded gases from the cylinder because of thevented construction of the cylinder and that because ,the vented gasesare at no time subjected to pump pressure, the fuel may readily enterthe cylinder. The reduced extension of the piston also acts as a trapfor the fuel, the selected clearance is such that there is nopossibility of fuel not being forced to the engine cylinder because ofcompression of gases at the end of the piston stroke, and neither willthe pump continue to force gases to the engine when no fuel is presentin the reservoir.

While a preferred embodiment of the invention has been illustrated anddescribed, it is understood that this showing and description areillustrative only and that the invention is not limited to the 50 formshown or described, or otherwise, except by the terms of the followingclaims:

What is claimed is: 1. A fuel pump comprising a cylinder having anoutlet in its top wall and a piston and a fuel 55 inlet arranged to beuncovered by said piston. means for forcing fuel to the cylinder, meansfor venting gases occluded in said cylinder during at least a portion ofthe time during .which a fuel charge is forced to the cylinder, saidventing 60 means including a reduced piston portion extending upwardlyin said cylinder having an opening adapted to be periodically connectedto the exterior of the cylinder venting means.

2. A fuel pump comprising a cylinder having an 65 outlet in its topwall, a piston and aA fuel inlet arranged to be uncovered by saidpiston, means for forcing fuel to the inlet, a main supply tank, areturn conduit from the pump to the tank and in open communicationtherewith, said cylinder 70 having an annular groove therein forconducting fuel leakage past the piston to the return conduit, and saidpiston having an upstanding reduced portion having a passage thereinconnecting said cylinder with the groove at the end -of eachv 75 suctionstroke.

a piston and a fuel inlet arranged to be uncovered by said piston, meansfor forcing fuel to the inlet,

'a main supply tank, a return conduit from the pump to the tank and inopen communication therewith, said cylinder having venting means thereinfor conducting' fuel leakage past the piston to the return conduit, saidpiston having a reduced portion extending above the cylinder inlet andprovided with a passage adapted to connect the cylinder with the ventingmeans while the inlet is uncovered by the piston.

4. A fuel pump comprising a substantially vertical cylinder having apiston, afuel inlet and a fuel outlet, means for venting the cylinder atthe termination of the inlet stroke comprisinga second outlet passagecontrolled by the piston and having its entrance above the fuel inletand below the rst outlet, means for trapping a quantity of` fuel in thecylinder, and said pump having a clearance volume which is less than thevolume of the trapped fuel.

5. A fuel pump comprising a cylinder having a piston, a fuel inlet and afuel outlet, means for venting the cylinder at the termination of theinlet stroke, means for trappingga quantity of` therein, said pistonhaving a reduced upwardly l extending portion provided with a conduitarranged to connect the groove with the interior of the cylinder duringthe suction stroke of the pump, said reduced portion defining with thecylinder an annular fuel space, the volume of which is greater than theclearance volume o1 the pump.

7. A ful pump comprising a substantially vertical cylinder having apiston, a fuel inlet and a fuel outlet, said cylinder having a ventedgroove therein, said piston having a reduced upwardly extending portionprovided with a conduit arranged to connect the groove with the interiorof the cylinder during the suction stroke of the pump, said reducedportion defining with the cylinder an annular fuel space the volume ofwhich is greater than the clearance volume of the pump, said pistonbeing arranged to uncover the fuel inlet and vent the cylinderconcurrently.

8. A liquid fuel pump comprising a cylinder having a fuel inlet, a fueloutlet and a piston, a spring loaded check valve in the outlet thespring pressure on the valve being such that in the absence of liquidfuel the compression of gas in the pump is insufficient to open thevalve, and means comprising an upstanding reduced piston portion havinga venting opening therein for trapping liquid fuel in the cylinder ateach suction stroke of the piston.

9. A liquid fuel pump comprising a cylinder having a fuel inlet, a fueloutlet and a piston, a spring loaded check valve in the outlet thespring pressure on the valve being such that in the absence of liquidfuel the compression of gas in the pump is insufficient to open thevalve, said piston having a standpipe thereon adapted to trap liquidfuel at each suction stroke of the pump, and means fox` venting thestandpipe dur-

